I don't know any other furniture store that comes close to having decent design and decent quality combined with decent prices and immediate delivery. Most other cheap end furniture stores have crappy design, lousy quality.
As of today, if you want to buy a sofa, IKEA is one of the very few furniture stores where you can actually pick up the sofa right away. It's also one of the very few furniture stores that doesn't promote a few items and then hikes up the prices of other items. Prices are consistently average or sort of low so that customers trust that they are not being screwed.
They are also great at having products for all price points. Even if you don't buy that sofa you are still likely to spend some money on napkins or towels or the meatballs.
And imaging being able to test a new product or pricing or design in one or two of your stores that you know to have average customers and then roll out the product all over the world.